I expect Rishkar to find multiple homes throughout Standard, and even being legendary is less of a drawback when an extra Rishkar can be cast to put a +1/+1 counter on two creatures
And yeah that mewtwo referenced by KEI is almost certainly the one Bulbapedia is talking about
While most creatures in the deck are a discard outlet aswell it still ended up being a good amount of pieces, not too hard because the deck is a pile of good cards and a combo, but Loner + Cauldron being a kill is an upgrade for sure
So much so, in fact, that the card could well become the most expensive card ever printed
Although prices for this card have fluctuated over the years, its still occasionally available in selected card shops, making it a desirable grab for fans of Pikachu, Zekrom, or collectors of seventh-generation cards
Since this is an attack trigger, you dont need to have Narset live long or even through combat, you just need that hexproof to keep her safe until your next combat set